Controlling device for engine driven compressor units



Feb. 24, 1953 c, s, B R 2,629,536

CONTROLLING DEVICE FOR ENGINE DRIVEN COMPRESSOR UNITS Filed Nov. 12, 1948 INVENTOR BCHARLES 8. El AKER HIS ATTORNEY- Patented Feb. 24, 1953 CONTROLLING DEVICE FOR ENGINE DRIVEN COMPRESSOR UNITS Charles S. Baker, Corning, N. Y., assignor .to-

Ingersoll-Rand Company, New York, N. Y., a corporation of New Jersey Application November 12, 1948, Serial No. 59,448

Claims.

This invention relates to compressor apparatus, and more particularly to a controlling device for combustion engine driven compressor units.

One object of the invention is to control the speed of the unit and, therefore, the discharge output of the compressor in accordance with the variations in the rate at which the discharge output of the compressor is consumed.

Another object is to minimize the number of periods of unloading and reloading of the compressor.

Qther objects will be in part obvious and in part pointed out hereinafter.

In the drawing accompanying this specification and in which similar reference numerals refer to similar parts,

Figure 1 is a side elevation, partly broken away, of a compressor unit equipped with a controlling device constructed in accordance with the practice of the invention, and

Figures 2 and 3 are vertical views, partly in section, of details of the invention.

Referring more particularly to the drawings, 2t designates the compressor and 2| the internal combustion engine of the unit having their respective shafts 22 and 23 connected together by a coupling 23.

The compressor 29 is shown as being of the multi-stage vertical type having a first stage cylinder 25 and a second stage cylinder 26 and pistons 2'! and 28, respectively therein for compressing the fluid medium which is delivered to the compressor by an inlet conduit 29 connected to a head it for the cylinders. The discharge output of the compressor passes from the head 3i through a conduit 3i connected to a storage receiver 32.

The admission of fluid into the cylinders 25 and .25 is controlled by suitable inlet valve mechanisms 33 arranged in the head 30. The head also contains discharge valve mechanisms 34 for controlling the discharge of compressed fluid from the cylinders into the head, and the head 33 may be provided with a suitable passage (not shown) to convey the fluid from the discharge valve of the low pressure cylinder to the inlet valve of the high pressure cylinder.

The load on the cylinders 25 and 26 is controlled by unloading devices 35 that operate to unseat the valve elements 35 of the valve mechanisms In the form shown each unloading device 35 comprises a piston 31 which is reciprocable in a chamber 33 in the upper Wall of the head 39 and depending fingers 39 on the, piston for engagement with the valve element 35. A

spring 40 interposed between the valve mechanism 33 and the piston 3'! normally holds the piston 31 in retracted position and the fingers 39 out of the engagement with the valve element 33.

The pistons 31 are actuated for unseating the valve elements 35by pressure fluid which is conveyed to the chambers 38 by a conduit 41 leading from an auxiliary valve mechanism 42 to which pressure fluid is conveyed from the receiver 32 by a conduit 43. The valve mechanism 42 comprises a casing 44 having an axial bore 45 the upper portion of which is in constant communication with the' conduit 63 and constitutes a pressure chamber 43. The chamber 46 opens at its lower end into a valve chamber 47, and at the juncture of the chambers is a beveled seat 48 for a valve 69 reciprocable in the chamber 41.

The valve 49 is normally held against the seat 48 by a spring'fifl encircling a guide rod 5| that extends into a recess 52 in the lower portion of the valve and has a coniform head 53 for pointengagement with the valve. The spring 5!] is calibrated to yield to a predetermined maximum receiver pressure. Its upper end seats against the coniform head 53 and the lower end against a shouldertd within a sleeve 55 which loosely encircles the guide rod 5! and is threaded into the lower end portion of the casing 44 for varying the force of the spring 50. More particularly, the sleeve 55 is in threaded engagement with a bushing 56' which is itself threaded into the casing 44 for adjustment endwise thereof and is provided at its upper end with a beveled seat 51 for a corresponding beveled seating surface 53 at the lower end of the valve 49.

The valve 49 isguided only by the guide rod 51 and is of smaller diameter than the chamber 47 to define a pathway for the passage of pressure fluid to the conduit 4| which opens into the valve chamber 41 at a point between the seats 48 and 5?. Near the upper portion of the valve is an external flange 59 whichis of slightly smaller diameter than the chamber 41 to partly restrict the flow of the pressure fluid passing to the conduit 4!, and the upper surface of said flange 59 constitutesa pressure surface 69 against which the fluid impingesat the instant communication is established between the chambers 46 and 41 to cause the valve to quickly nap downwardly against the seat 51 and thereby prevent the loss of pressure fluid through the bushing 55 andthe sleeve 55 to the atmosphere.

In practice, the upper end of the valve 49 is constantly subjected to the force of the pressure in the chamber :26, this being receiver pressure,

and the spring 50 is adjusted to yield to a certain predetermined maximum receiver pressure. Thus, when the pressure fluid in the chamber 46 reaches that certain predetermined maximum value it will unseat the valve 49 and, striking against the flange 59, will cause the valve 49 to be quickly moved downwardly against the seat and to be held in that position by the pressure of the fluid acting against the upper end of the valve and the pressure surface 60. Pressure fluid will then flow from the valve chamber 41 through the conduit 4| into the chambers 33 against the piston 31 and cause the fingers 39 to unseat the valve elements 36.

In this way, the compressor cylinders will be unloaded and will remain thus until the receiver pressure falls below the force exerted by the spring 56 and the spring 50 will then act to shift the valve 46 against the seat 48 and cut-off the communication between the storage receiver and the conduit 4!. The pressure fluid will then exhaust from the chambers 38 through the conduit M into the chamber 41, thence through the space between the seat 51 and the seating surface 58 and through the bushing 56 and the sleeve 55 to the atmosphere. At the same time the springs 46 will move the fingers 39 out of engagement with the valve elements 36 which will then again function in the normal manner to control fluid admission into the compressor cylinders.

The internal combustion engine 2| driving the compressor may be of a conventional type, having the usual inlet and exhaust manifolds 6i and 62, an inlet conduit 63 connecting a carburetor 64 to the inlet manifold and a butterfly valve 65 in the conduit 63 for controlling the fuel supply to the engine. Movement is transmitted to the valve 65 for setting it in its different fuel controlling positions by arod 66 which is pivotally connected at one end to the valve 65 and at its other end, in like manner, to a lever 61 aflixed to the shaft '68 of a rocker arm 69 which seats against the speed governor 19 of the engine 2|. The governor, which is shown positioned .at an end of the engine to be driven by its crankshaft through a suitable gear train H, is of the well known type having centrifugally actuated arms 12 pivotally connected to the driven gear of the train H to act against a sleeve T3 which is slidable upon a shaft 14 on the driven gear and constantly abuts the free end of the rocker arm 69 for tilting said rocker arm. The arrangement of these parts is such that they tend to rotate the butterfly valve 65 for diminishing the fuel supply to the engine when its speed exceeds a certain predetermind maximum rate and to permit the valve 65 to move in the reverse direction for increasing the fuel supply to the engine.

Normally, however, the speed of the engine and, therefore, the output of the compressor are controlled entirely by mechanism acting responsively to the pressure Within the receiver 32. This mechanism, in a preferred form, comprises a regulator the casing of which consists of an intermediate body l5, a plate-like cover H at one end of the body and a dome-shaped cover 1 8 at the opposite end. The body 16 is recessed in the side confronting the cover 18 to provide a chamber 19 which is in constant communicaticn with the receiver 32 through a conduit 89, and its outer end is sealed by a diaphragm BI that is clamped at its marginal portion between the body 16 and the cover 18.

The opposite end of the body 16 is likewise recessed to provide a chamber 82 which is in constant communication with the atmosphere through a passage 83 in the body l6 .and an orifice 84 in a plug 85 threadedly connected to the body. The outer end of the chamber 82 is sealed by a diaphragm 86 clamped between the body and the cover 11, and pressure fluid for actuating the diaphragm 86 passes to the chamber 82 from the chamber 19 through an orifice 8! in the end of a cup-shaped member 88 threaded, in inverted position, into the wall 89 separating the chambers 19 and 82 from each other.

The effective area of the orifice 31 is determined by a metering pin 90 in the member 88 and movable axially thereof. The pin 90 ex tends into .the orifice 8! and is of conniform shape so that when it rises within the member 88 said pin decreases the flow area of the orifice and increases the area of communication between the chambers 1982 when moving in the opposite direction.

The pin 96 has a shoulder 9| at the large end of its coniform portion to serve as a seat for a spring 92 which rests at its other end on a spring seat 93 in the lower end of the member 83 and tends constantly to urge the pin 96 upwardly for closing the orifice 81. The spring seat 93 is retained within the member 88 by a retainin ring 94 seated in the lower end of the member 8-8 and has suitable perforations 95 for the passage of pressure fiuid from the member 88 into the chamber 82.

The spring 62 is capable of exerting a force sufIicien-t to retain the pin 83 in position to close the orifice 81 against the pressure in the chamber 19, and the downward or opening movement of the pin 90 is effected by the diaphragm 8| which has attached to its underside a plate 9% to overlie and engage the end of the pin 90, The plate 86 has a stem 9? extending throughthe diaphragm, and a nut 98 threaded onto the stem 9'! serves to clamp the diaphragm 3! between the plate 95 and a washer 99 interposed between the nut 98 and the diaphrgam. The Washer 99 also serves as a seat for an end of a spring $00 the opposite end of which bears against a plate lei on the lower end of a screw I92 threaded through the outer end wall of the dome-shaped cover 16 for selectively varying the force of the spring I00.

In the relaxed position of the diaphragm 8|, as when the pressure within the chamber 19 is of ll'lSllfi'lCiGIlt value to raise the diaphragm against the force exerted by the spring we, the plate 96 rests upon the end of the member 88. In order, therefore, to prevent said plate from blocking off the orifice 8'! the outer end surface ms of the member 88 is rounded and a radial groove, or grooves, I04 is formed in the end of the member 88 to afford constant communication between the chamber 19 and the orifice 8'! to supply pressure fluid to the chamber 82 for actuating the diaphragm 86.

Such movement of the diaphragm serves to normally actuate the butterfly valve 65 and is transmitted thereto by linkage designated in its entirety by Hi5 and connected to the lever 61. This linkage comprises a bell crank [66 which is pivoted at its angle on a pin it? seated in a lug 08 at the side of the cover 11. One arm I09 of the bell crank extends part-way along the cover ii and has an upwardly directed portion H6 that extends into a recess iii in the cover and terminates in a plate portion IE2 that lies perpendicular to the portion H0 and bears against the underside of the diaphragm 86.

Suitable stop means are provided to limit the degree of movement of the bell crank I06 and to determine the limiting positions of the valve 05. To this end the cover is provided on its inner surface with an upwardly extending projection II3 which the underside of the plate II2 engages when in its lowermost limiting position, and which position corresponds with the maximum speed setting of the valve 05. Ihe opposite limiting position to which the bell crank I05 may move is determined by a stop member in the form of a bolt II 4 threaded into the arm I09 to abut the underside of the cover 11. The bolt H4 is threaded into the arm I09 and is, therefore, readily adjustable in the arm to vary the degree of movement of the bell crank and thus, of course, also of the valve 65, In the present instance, however, it is intended that the bolt be so adjusted that when it engages the cover I! the valve 05 will occupy a position to cause the engine 2i to operate at a predetermined intermediate rate or" speed as for example, one half the predetermined maximum speed.

The free end of the other arm H5 is pivotally connected to a transmission member which is designated in its entirety by M6 andcomprises a rod III that is pivotally connected to an intermediate portion of a rocker IIO pivoted at its lower end to a lug II9 adjacent the base of the engine 2|, the upper end of the rocker II 8 being connected to an end of a helical tension spring I20 the opposite end of which is connected to the intermediate portion of the lever 61 for holding the rocker arm 09 against the sleeve I3. Owing to this arrangement the thrust of the rocker I I8 is transmitted through the spring I20 to the lever 61 and thus to the valve 05.

The spring I20 also serves as the engine governor spring and is calibrated to predominate over the force exerted by the governor arms I2 throughout the entire speed range between the predetermined intermediate and the predetermined maximum speeds and to yield to the force of the governor arms for controlling the throttle valve only in the event that the engine speed exceeds the predetermined maximum rate. Thus, as will be understood, the throttle valve 05 is entirely under the control of the regulator I5 during the normal operation of the unit and the governor I assumes control of the throttle valve 0 only in the event that, for some cause, as for example, the faulty adjustment of any of the parts, the speed of the engine exceeds the predetermined maximum rate in an undesirable degree.

In order to obviate a speeding-up of the engine 2I at the instant the compressor 20 is unloaded, such as might otherwise occur in a given setting of the valve 65 when the compressor is suddenly unloaded, the transmission member IE0 is provided in its organization with a fluid actuated adjustor IZI that serves to impart to the valve 65 the closing movement required to prevent the acceleration of the engine. The adjustor comprises a casing I22 having a stem I23 at one end which is pivotally connected to the free end of the arm H by a pin I24. Within the casing I22 is a chamber 525 to which pressure fluid is conveyed from the conduit II by a conduit I20. The pressure fluid thus introduced into the chamber I25 serves to actuate a reciprocatory piston I2! which is threadedly connected to the end of the rod Ill.

The piston I21 is normally retained in its retracted position by a spring I28 that acts at 6 one end against the piston and at the other end against a flange I29 on the periphery of a bushing I30 extending into the open end of the cham-' ber I25. The flange I29 rests upon a retainer ring I 3I embedded in the wall of the chamber I25 and is held thereagainst by the spring I28. In order to limit the degree of movement of the piston I21 to the extent required for imparting such slight degree of compensatory movement to the valve 65, a stop member I32 in the form of a sleeve encircling the rod II! is threaded into the bushing I30 to position its inner end I33 in suitably spaced relation with respect to the piston I21 to serve as a stop therefor.

In practice, and at the beginning of an op erating period of the compressor 20 against an empty system, and with the spring I20 fully contracted, the linkage I05 will hold the butterfly valve 65 in a position to supply fuel to the engine at the rate required for operating it at the predetermined high rate and will hold the bolt II4 against the cover II. The metering pin 90 is than fully retracted to permit a maximum area of communication between the chambers I9 and 82 through the orifice 81. The bell crank I00 will then also occupy a position wherein the bolt I I4 seats against the cover 11, this being the position of the bell crank that corresponds to the setting of the valve 65 for operating the engine at the predetermined high speed and also to determine the starting speed of the engine.

Under these conditions, pressure fluid discharged into the storage receiver 32 will flow into the chamber I9 and through the orifice 31 into the chamber 82. A portion of such pressure fluid will, of course, escape from the chamber 82. to the atmosphere through the passage 83 and the orifice 84. However, as the pressure in the chamber 82 rises it will depress the diaphragm 86 and rock the bell crank I06, about the pivot I0! to move the plate portion I2 in the direction of the projection H3, and when the pressure in the chamber 82 reaches a value of, say, twentyflve pounds per square inch the diaphragm will be fully depressed. This movement of the bell crank is transmitted to the valve I35, by the linkage I05, the lever 01 and the rod 68 for opening said valve to the position required for operating the engine at the predetermined maximum speed. In this speed position of the vaive 05 the plate portion H2 rests upon the projection H3 and the valve 05 will remain stationary so that the speed of the engine will remain at a substantially constant rate.

The unit will continue to operate in the manner described until the pressure within the storage receiver 32 and, therefore, in the chamber 19 reaches that predetermined high value, say 100 pounds, at which it will overcome the force exerted by the spring I00 against the diaphragm 8!. If, thereafter the pressure in the chamber It continues to increase, the diaphragm III will rise and the pin 90 will also move upwardly under the force of the spring 92 and reduce the effective flow area of the orifice 8T accordingly. At the same time pressure fluid constantly passes from the chamber 82 through the orifice 8 to the atmosphere so that the pressure within the chamber 82 decreases progressively, both by reason of the decreasing flow area of the orifice 3? and the constant bleeding off of pressure fluid to the atmosphere from the chamber 82.

When the pressure in the chamber 82 has been reduced to a lower value than the force exerted by the governor arms 12 the said arms will quired to reduce the fuel supply to the engine.

and will also rock the bell crank Hi6 about the pivot it? to cause said bell crank to follow the upward movement of the diaphragm 85. If, during such upward movement of the diaphragm, the demand on the pressure fluid in the storage receiver 32 increases and causes the receiver pressure to fail the diaphragm 8! will descend responsively thereto and depress the pin 98 to again increase the flow of pressure fluid into the chamber 82 for shifting the valve 55 to accelerate the speed of the engine.

If, on the other hand, the receiver pressure continues to rise say, to a predetermined maximum value of 105 pounds, the diaphragm ill and the pin 96 will rise and reduce the supply of pressure fluid to the chamber 82 accordingly, r possibly cut-off the flow of pressure fluid through the orifice Bl into said chamber altogether. The bell crank will then swing about the pivot is to seat the bolt H4 against the cover i? and to place the butterfly valve 55 in the position required to cause the engine to operate the predetermined high speed, thereby reducing the output of the compressor 2!].

The compressor unit will continue to operate at the reduced speed and the pressure in the re ceiver 32 to increase and fall in accordance with variations in demand. However, if the receiver pressure continues to rise and exceeds the force exerted by the spring 50, of the valve mechanism 42, it will unseat the valve 59. The pressure fluid thus admitted into the chamber against the pressure surface 60 will then quickly drive the valve downwardly against the seat 57. At the same time, pressure fluid will flow through the conduit 4i into the chambers 38 and drive the fingers 39 against the valve elements 323 of the inlet valve mechanisms for unseating them. The compressor will then be fully unloaded.

Simultaneously with the valving of pressure fluid to the inlet valve mechanisms pressure fluid will flow through the conduit I26 into the chamber I of the fluid actuated adjustor i2! and drive the piston l2'i against the stop E33. This movement of the piston I21, transmitted through the linkage connecting it with the valve 65, will impart a further slight degree of closing movement to the valve 65 and thereby obviate an increase of speed such as ordinarily occurs in a given setting of the power controlling valve of an engine following the removal of the load from a compressor.

The parts controlling the load on the cornpressor and the speed of the engine will remain in the positions described as long as the pressure in the receiver exceeds the force of the spring but when it falls below that value the spring 58 will return the valve 49 to the seat 48. The pressure fluid in the cylinders will then escape through the conduit 4| into the valve chamber 5?, thence through the space between the lower end of the valve 49 and the seat 51 and through the bushing 55 and the sleeve 55 to the atmosphere. At the same time, the pressure fluid in the chamber I25 will also escape through the conduits [26-55 and through the valve mechanism 42 to the atmosphere. The spring I28 will then retract the piston l2'! and thus move the valve 55 to the predetermined high speed controlling position.

If, thereafter, the pressure in the receiver falls to a value that permits the diaphragm 8| to descend upon the pin 99 and open the orifice 8T,

pressure fluid will again flow into thechamber 82 and whenthe pressure therein reaches a value capable of overcoming the force of the governor arms 12 it will shift the valve 65 for increasing the engine speed. And when the pressure in the chamber 19 reaches a value below that exerted by the spring I09 the diaphragm 8| will descend to open the pin to wide limits. The pressure fluid thereafter admitted into the chamber 82 will move the plate H2 against the projection i l3 and position the valve 65 for operating the engine 2| at maximum speed.

In practice, the present invention has been found highly desirable for controlling the operation of a compressor unit serving to supply the power demands of a group of machines that are operated intermittently, as for example rock drills, since, when the receiver pressure has attained the value necessary for the eflicient operation of such machines the speed of the engine is automatically decreased or increased in accordance with the demands imposed by such intermittent operation of the rock drills. And if the demand upon pressure fluid supply is insufficient to maintain the storage pressure below a certain predetermined value the controlling device will operate to cause the engine to run at the predetermined lower rate of speed, thereby lowering the output of the compressor which will continue operating at the lower speed until the receiver pressure reaches the predetermined maximum value at which the compressor is unloaded.

'I claim:

1. In a controlling device for an internal combustion engine and a compressor driven thereby, a throttle valve for controlling the fuel supply for the engine having limiting positions corresponding to predetermined high and maximum engine speeds, a fluid actuated member serving as the sole power actuator for shifting the throttle valve, linkage for transmitting movement from only the fluid actuated member to the throttle valve and to initially hold the throttle valve in an open position for causing operation of the engine at such predetermined high speed, valve means for varying the supply of pressure fluid to the fluid actuated member, control means operatively engaging the valve means acting constantly responsively to pressure variations in the compressor discharge pressure above a certain predetermined high value to vary the position of the valve means and thereby the position of the fluid actuated member for varying the speed-setting of the throttle valve in accordance with variations in the discharge pressure of the compressor and to cut-off the supply of pressure fluid to the fluid actuated member when the discharge pressure reaches a predetermined maximum value, and means yieldingly opposing the maximum speed movement of the fluid actuated member to position the throttle valve for operation of the engine at such predetermined high speed upon the attainment of the predetermined maximum discharge pressure.

2. In a controlling device for an internal combustion engine and a compressor driven thereby, a throttle valve for controlling the fuel supply to the engine having limiting positions corresponding to predetermined high and maximum engine speeds, a fiuid pressed member serving as the sole power actuator for the throttle valve, linkage for transmitting movement from only the fluid pressed member to the throttle valve and to initially hold the throttle valve in an open position for causing operation of the engine at such predetermined high speed, means for varying the supply of pressure fluid to the member for shifting the throttle valve to and holding it immovable in the'maximum speed-setting, means in engagement with the first mentioned means acting responsively to compressor discharge pressure of a predetermined high value and to variations of pressure between such predetermined high pressure and a predetermined maximum discharge pressure for varying the position of the first said means and thereby varying the supply of pressure fluid to the member to change the speed-setting of the throttle valve in accordance with variations in the compressor discharge pressure, and means yieldingly opposing maximum speed movement of the throttle valve and acting to move the throttle valve to the predetermined high speed-setting whenever the pressure against the member falls below the force exerted by the last said means.

3. In a controlling device for an internal combustion engine and a compressor driven thereby, a throttle valve for controlling the supply of fuel to the engine having limiting positions corresponding to predetermined high and maximum engine speeds, afluid pressed member serving as the sole power actuator for the throttle valve, linkage connected to the throttle valv associated with and actuated by only the member and serving to initially hold the throttle valve in an open position for causing operation of the engine at such predetermined high rate of speed, valve means for varying the supply of pressure fluid to the member for moving the throttle valve from the predetermined high speed-setting to and holding said throttle valve in the maximum speedsetting, means acting responsively to a predetermined high compressor discharge pressure engaging the valve means for varying the position of said valve means and thereby varying the sup ply of pressure fluid to the member for shifting the throttle valv in accordance with variations in the discharge pressure between such predetermined high value and a predetermined maximum value and to cut-off the supply of pressure fluid to the member when the discharge pressure reaches such predetermined maximum value, and means yieldingly pressing against the linkage to oppose the maximum speed movement of the throttle valve and acting to move the throttle valve to the predetermined high speed-setting whenever the pressure acting against the member falls below the force exerted by the last said means.

4. In a controlling device for an internal combustion engin and a compressor driven thereby, a throttle valve for controlling the fuel supply to the engine having limiting positions corresponding to predetermined high and maximum engine speeds, linkage connected to the throttle valve for shifting said valve and to initially hold said throttle valve in an open position for causing operation of the engine at such predetermined high speed, a fluid pressure actuated member for holding the linkage immovable to position the throttle valve for operation of the engine at the predetermined maximum speed until the compressor discharge pressure reaches a predetermined high value and serving as the sole power actuator for the throttl valve and the linkag valve means for valving pressure fluid to the member acting responsively to compressor discharge pressure in excess of such predetermined high value to vary the value of the pressure acting against the member and to cut-off the supply of pressure fluid to the member whenever the compressor discharge pressure reaches a predetermined maximum value, and means yieldingly pressing against the linkage to oppose the maximum speed movement or" the throttle valve and acting to move the throttle valve to the predetermined high speed-setting whenever the pressure acting against the member falls celow the force exerted by the last said means.

In a controlling device for an internal combustion engine and a compressor driven thereby, a throttle valve for controlling the supply of fuel to the engine having limiting positions corresponding to predetermined and maximum engine speeds, linkage connected to the throttle valve to initially hold said throttle valve in an open position for causing operation of the engine at such predetermined high speed and to move the throttle valve to the maximum speed-setting, a pressure fluid. actuated member acting against the linkag and serving as the sole actuator for moving the throttle valve to and holding it in the maximum speed-setting, valve means for varying the supply of pressure fluid to the member, means associated with the valve means acting responsively to compressor discharge pressure of a predetermined high value and to variations of pressure between such predetermined high pressure and a predetermined maximum discharge pressure for varying the position of the valve means and thereby varying the supply of pressure fluid. to the member to change the speed-setting of the throttle valve in. accordance with variations in value of the compressor discharge pressure and to cut-oil th supply of pressure fluid to the member when the discharge pressure reaches the predetermined maximum value, and means yieldingly pressing against the linkage to oppose the maximum speed movement of the throttle valve and acting to move the throttle valve to the pre determined high speed-setting whenever the pres sure acting against the member falls below the force exerted by the last said means.

CHARLES S. BAKER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,009,659 Hill July 30, 1935 2,166,789 Baker July 18, 1939 2,171,286 Baker Aug. 29, 1939 2,212,631 Baker Aug. 27, 1940 2,225,854 Baker Dec. 24, 1940 2,294,410 Lamberton Sept. 1, 1942 2,380,226 Frantz July 10, 1945 2,454,363 Wineman Nov. 23, 1948 2,546,613 Paget Mar. 27, 1951 

